Apparatus for reducing the dissolved gas concentration in a liquid

ABSTRACT

Apparatus for reducing the dissolved gas concentration in a liquid, for example, a liquid flowing in chromatographic system, utilizing the ability of the gas dissolved in the liquid to pass through a gas permeable membrane. The liquid is exposed to one surface of the membrane and the opposite surface of the membrane is provided with a coating of gas-soluble substance for increasing the permeability of the membrane and thereby enhancing the permeation of the gas through the membrane. Further, in various embodiments of the invention, a chamber is provided opposite or surrounding the coated membrane and, in accordance with the teachings of the present invention, the chamber may be vented to the atmosphere, evacuated and sealed or communicated to a means for establishing a pressure in the chamber sufficiently lower than the pressure of the liquid exposed to the membrane such that the permeation of the gas through the membrane is enhanced. Additionally, the chamber may be provided with absorbent or adsorbent material for accommodating gas permeated through the membrane.

Waited tiates g i 51 Aug. 14, 1973 APPARATUS FOR REDUCING 1E DJISSOLVEDGAS CONCENTION W A Primary Examiner-Samih N. Zahama LIQUID AssistantExaminer-Richard W. Burks [75] inventor: Robert W. Allington, Lincoln,Nebr, Attorney vmcem Carney [73] Assignee: instrumentation Smcialties[57] SACT Company Lmcoln' Nebr' Apparatus for reducing the dissolved gasconcentration [22] Fil d; A 26, 11971 in a liquid, for example, a liquidflowing in chromatographic system, utilizing the ability of the asdissolved [21] Appl' 137381 in the liquid to pass through a gaspemfeable membrane. The liquid is exposed to one surface of the mem- 52111.5. c1. 55/158, 55/189 brene and the pp Surface of the membrane is p51 1111. 1:1 B011! 13m vided with a coating of gee-soluble substance for[58] 1mm 61 Search 55/l6, 158, 189; creasing the permeability of themembrane and thereby 1 17/161 ZA; 210/2143, 321, 433 456 enhancing thepermeation of the gas through the membrane. Further, in variousembodiments of the inven- [56] Referen e (m d tion, a chamber isprovided opposite or surrounding the UNITED STATES PATENTS coatedmembrane and, in accordance with the teach- 3 556 302 H1971 A "mat210/433 X ings of the present invention, the chamber may be 3 367 8502/1968 Jo hnsonKI 3223i. 55/158 x vented 9 the ammphere' evacuaied. andsealed 9 3:560:377 1,1969 Loeffler 210/433 X communicated to a means forestablishing a pressure 1n 3,591,493 7/1971 Zeineh 210/433 x the chambersufficiently lower than the Pressure of the 3,614,856 10/1971 Sanz etal. 55/158 x liquid exposed to the membrane Such that the P 3,668,8376/1972 Gross 55/158 ation of the gas through the membrane is enhanced.3,335,545 8/1967 Robb et a]. 55/158 X Additionally, the chamber-may beprovided with absor- 2, 1958 De Ressett- 55/16 bent or adsorbentmaterial for accommodating gas per- 3,332,216 7 1967 Stern 55/158 meatedthrough the membrane 3,396,510 8/1968 Ward et al.. 55/16 3,625,73412/1971 Ward 55/158 X 30 Claims, 7 Drawing Figures A-VACUUM PUMPB-VENTED TO ATMOSPHERE C- EVACUATED AND SEALE D Patented Aug. 14, 19733,751,879

Sheets-Sheet l FIG.1

A-VACUUM PUM P B-VENTED TO ATMOSPHERE C-EVACUATED AN SEALED v INVENTORROBERT W. ALLINGTON A-VACUU M PUMP BY B-VENTED TO I ATMOSPHERE M M C-EVACUATED AND SEALE D ATTORNEYS Patented Aug. 14, 1973 3,751,879

3 Sheets-Sheet 2 FIG.3

-VACUUM PUMP 3 .f- 70 B-VENTED T0 ATMOSPHERE in C-EVACUATED 73 E ANDSEALED INVENTOR ROBERT W. ALL NGTON ATTORNEYS Patented Aug. 14, 19733,751,879

3 Sheets-Sheet 5 A-VACUU M PUMP B-VENTED TO ATMOSPHERE C- EVACUATED ANDSEALED INVENTOR ROBERT W. ALLI NGTON ATTORNEYS APPARATUS FOR REDUCINGTHE DISSOLVED GAS CONCENTRATION IN A LIQUID BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to apparatusfor reducing the concentration of gas in a liquid, and in particular, toapparatus for reducing the concentration of gas dissolved or included ina liquid flowing, for example, in chromatographic systems,spectrophotometric systems, specific ion analysis systems, or thermalconductometric analysis systems, to prevent the dissolved or includedgas from nucleating into bubbles.

2. Description of the Prior Art There are numerous instances in thevarious arts such as noted by way of example in the above Field of theInvention, wherein it is useful, necessary, or highly desirable toreduce the concentration of a gas in a liquid, in particular, a gasdissolved or included in a liquid. For example, chromatographic systemsoften use optical means to monitor the liquid or eluate emanating fromthe separating apparatus. However, optical monitoring devices areextremely susceptible to error from spurious refraction readings whichresult from the presence of gas in the eluate. For example, theinterfaces between the eluate liquid and the gas dissolved in the eluatewill significantly change the refraction readings of the eluate, and ifthe dissolved gas nucleates into bubbles, the refraction readings arefurther changed and worsened with regard to validity. To insure theaccuracy of the optical monitoring devices in chromatographic systems,it is necessary that all entrainedgas bubbles and as much dissolved gasas possible be removed from the eluate of the chromatographic system.

In the past, the problem has been typically approached by efforts toprevent liquids with entrained or dissolved gases from entering into thechromatographic system, i.e.,the liquid was treated prior to enteringthe system to drive out any possible gas. The treatment often consistedof boiling or evacuating bulk quantities of the liquid to be used.However, these methods only minimized the bubble formation problem inchromatographic apparatus, because quite often, the material used topack the chromatographic separating systems contains quantities of gason its surface regardless of any preliminary flushing with degassingsolvents or any other treatment that can be used to remove the dissolvedgas.

Still another prior art method of degassing the stream of liquid in achromatographic column was based on the principle of floatation orbuoyancy. In this approach the liquid stream is allowed to enter achamber at the same pressure as the optical cell and the dissolved gaseswould form bubbles and float up to a collection chamber. This has provengenerally unsatisfactory because the bubbles may not form in the properplace for extraction, and further, no means are available to extract thedissolved gases from the liquid-filled system. This approach also causesunwanted broadening of zones or peaks of dissolved solid material beingcarried by the liquid stream.

A preferred solution to the problem of removing the gas from or reducingthe gas concentration of, the eluate of a chromatographic system, wouldbe to treat the eluate intermediate the separating system and theoptical monitoring device, rather than treating the eluate prior toentering the separating system. However, apparatus by which thistreatment could be accomplished has not heretofore been available.

For example, the gas separation devices disclosed in US. Pat. Nos.3,246,449, 3,246,450 and 3,463,615 are not wholly satisfactory forremoving gas from, or reducing the gas concentration of, the eluate of achro matographic system.

SUMMARY OF THE INVENTION To overcome the problems of the prior art setforth above, the present invention sets forth apparatus for reducing thegas concentration in a liquid, wherein, in one embodiment of the presentinvention, the gas is exposed to one surface of a gas permeable membraneand the opposite surface of which membrane is provided with agas-soluble coating for increasing the permeability of the membrane, thegas permeates through the membrane with the permeation thereof beingenhanced by the gas-soluble coating. The gas-soluble coating may be afilm of a solid or liquid in which the gas is appreciably soluble;silicone and fluorosilicone liquids and solid compounds being taught. Inanother embodiment of the present invention, the liquid to have the gasconcentration therein reduced, for example the eluate from achromatographic column, passes through a flow passage having at leastone wall fonned from at least a portion of a gas permeable membrane. Theflow passage may be advantageously shaped in such a manner as tomaximize the surface contact between the eluate and the permeablemembrane. In various embodiments of the invention, a chamber may beprovided opposite or surrounding the flow passage and in accordance withthe teachings of the present invention, the chamber may be vented to theatmosphere, evacuated and sealed, or may be communicated with means forproviding a pressure in the chamber sufficiently lower than the pressurein the liquid in the flow passage so as to enhance the permeation of thegas through the membrane. The surface of the membrane exposed to thechamber is provided with a gas-soluble coating for increasing thepermeability of the membrane and for 'enhancing the permeation of thegas through the membrane. In various embodiments of the invention thecoated membrane is self-supporting, and in other embodiments of theinvention, support means in contact with the coated permeable membraneare provided to insure the dimensional stability of the flow passageupon the establishment of the above-mentioned pressure differential. Thesupport means are made from a rigid porous material which will offervery little or no resistance to the passage of the gas therethrough and,therefore, will not inhibit the removal of the gas through the gaspermeable membrane.

Accordingly, it is broadly the primary object of the present inventionto provide new and useful apparatus for reducing the concentration ofgas in a liquid.

It is a specific objectof the present invention to provide apparatus forremoving gas from a liquid in such a manner that the gas cannotrecombine with the liquid.

Still another object of the present invention is to provide apparatusfor reducing the concentration of gas in a liquid, which apparatus iscapable of handling corrosive liquids.

Still another object of the present invention is to provide apparatusfor reducing the gas concentration in the eluate in a chromatographicsystem which minimizes longitudinal mixing of the flow stream duringoperation of the apparatus.

Still another object of the present invention is to provide apparatusfor reducing the gas concentration in the eluate in a chromatographicsystem which apparatus preserves the integrity of the eluate contentdistribution by not disturbing the peaks or zones of solute in theeluate.

Other objects and advantages will be apparent from the followingdescription of several embodiments of the invention and the novelfeatures will be particularly pointed out hereinafter in connection withthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view,partially broken away, showing apparatus for reducing the gasconcentration in a liquid, built in accordance with the teachings of thepresent invention.

FIG. 2 is another embodiment of an apparatus for reducing the gasconcentration in a liquid built in accordance with the teachings of thepresent invention, having a cylindrical configuration.

FIG. 3 is a top plan view in section of another embodiment of anapparatus built in accordance with the teachings of the invention,having a spiral flow path for the liquid.

FIG. 4 is a front elevation, in section, taken along lines 4-4 of FIG.3.

FIG, 5 FIG. a top plan view, in section, of another embodiment of anapparatus built in accordance with the teachings of the invention,having a serpentine flow path for the liquid.

FIG. 6 is a top plan view, in section, of another embodiment of anapparatus built in accordance with the teachings of the invention,having a labyrinth flow path for the liquid.

FIG. 7 is a perspective view, partially broken away, showing apparatusfor removing gas from liquids built in accordance with the teachings ofthe present invention, having a cylindrical configuration as theembodiment shows in FIG. 2 and including a self-supporting gas permeablemembrane.

DESCRIPTION OF THE PREFERRED EMBODIMENT Although the invention isdescribed herein as applied to chromatographic systems, it will beunderstood, as noted above, that the invention is not restricted to thisuse and that there are many other applications in which the inventioncan be effectively utilized.

FIG. 1 shows an apparatus, for reducing the gas concentration in theeluate from a chromatographic system, in the form ofa housing orcontainer, generally indicated at 10, having vertically aligned firstand second sections, 12 and 14 respectively, secured together by aplurality of bolts 16. Between upper first section 12 and lower secondsection 14 of the apparatus is a gas permeable membrane 18 whosefunction will be explained in greater detail below. The upper section 12and lower section 14 of housing or container are provided with cavities20 and 22, respectively, which cavities are separated by the permeablemembrane 18.

Cavity 20 in upper section 12 is a comparatively deep recess, with anenlarged portion 24 at the bottom face of the section opposing the lowersection of the housing. Enlarged portion 24 of cavity 20 holds a layer26 of rigid, porous material, which is used to support permeablemembrane 18. The portion of the cavity above support means 26 in theupper portion 12 of housing 10 forms, in cooperation with permeablemembrane 18, a chamber 28 which, for example, may be communicated bytube 30 to a vacuum pump as indicated at A and the corresponding legendshown in FIG. 1. Alternatively, the tube, as indicated at B and C inFIG. 1, may be vented to the atmosphere or may be evacuated and sealed.It will be understood by those skilled in the art, that the specifictermination of tube 30 will depend upon various known considerations,e.g., the pressure level of the liquid to have its gas concentrationreduced, the expected volume of gas to be removed, the environment inwhich the degassing apparatus is located, and the chemical nature of thegas to be removed. Another alternative within the contemplation of thepresent invention is that the chamber 28 may, or may not be evacuated,depending upon various of the foregoing considerations, and the chambermay be provided with absorbent or adsorbent material 29 foraccommodating the gas removed from the liquid; such adsorbent orabsorbent material being chosen, as understood by those skilled in theart, for its compatibility with the gas to be removed.

The surface of the membrane 18 exposed to the chamber 28 is providedwith a coating 19 for increasing the gas permeability of the membraneand for enhancing the permeation of the gas through the membrane. Thecoating 19 may be a substance or film of gassoluble solid or liquid inwhich the gas to be passed through the membrane is appreciably soluble,for example, such film may be a film of silicone liquid or a film offluorosilicone liquid. Also, the coating 19 may be a film of solidsilicone compound or a film of solid fluorosilicone compound. The reasonwhy such a coating increases the gas permeability of certain membranes,and enhances the permeation of gas therethrough, is not completelyunderstood, however, it is believed that such a gas-soluble coatingaffects certain surface energy characteristics of the membrane thatwould otherwise prevent the gas from leaving the membrane and passinginto the chamber 28.

The recess 22 in the lower portion 14 of container 10 fonns, incooperation with permeable membrane 18, a flow passage 32 for thechromatographic system eluate which is to have its gas concentrationreduced. The eluate enters the flow passage 32 through the substantiallyvertical inlet conduit 34 extending perpendicularly through lowersection 12 into the flow passage. Once in the flow passage, thesubstantial portion of the eluate will be in direct surface contact withthe permeable membrane 18 as the eluate flows from inlet tube 34 to anoutlet tube 36 disposed substantially parallel to the inlet tube inhousing 10. At least a portion of the gas dissolved in the eluate willpenneate through the membrane 18 and the coating 19 and into the chamber28 with the permeation being enhanced by the coating 19. Thus the gasconcentration in the eluate flowing through the flow passage 32 isreduced.

The depth of cavity 22 in lower portion 14 of housing 10 is much smallerthan the depth of cavity 20 in upper portion 12 of the housing whichforms chamber 28. Ideally, the depth of flow passage 32 should be nogreater than the minimum thickness necessary to allow for the flow of afilm of eluate through the apparatus so as to maximize the exposure ofthe eluate to the membrane. Further, the flow passage is relatively longcompared to its cross-sectional area (width and depth) so thatlongitudinal mixing of the flowing liquid eluate is minimized.

Support means 26 plays an important role in certain embodiments of thepresent invention, since in some instances the permeable membrane 18must be fairly thin, yet wide in area, to allow passage or permeatingrequired in chamber 28 in order to provide the pressure differentialnecessary to induce a flow of the gas in the eluate across the permeablemembrane. Therefore, the critical thickness dimension of the flowpassage could be readily affected by distortion of the membrane causedby the pressure differential were it not for the means to support themembrane. Under such condition, the support means 26-is provided and ispositioned in enlarged portion 24 of the upper recess 30 to insure thepositive positioning of the membrane and, therefore, also insure thatthe dimensions of the flow passage will not change as the pressure inthe chamber may be increased or decreased.

OTHER EMBODIMENTS OF THE INVENTION FIG. 2 shows another embodiment ofthe present invention. In this embodiment, the housing or container 40of the apparatus for reducing the gas concentration in a liquid includesa cylindrical section 42 having end walls 44 and 46 respectively. Atubular gas permeable membrane 50, coaxially disposed with relation tothe axis of the cylindrical section 40, extends through openingsprovided in the end walls 44 and 46 of the container. Support means,comprising an annulus of porous, rigid support material 52, isconcentrically disposed about and in engagement with the permeablemembrane 50 over the length of the membrane within container 46. Thesupport material runs from front end 44 to rear end 46 of container 40and has a diameter substantially smaller than the diameter of container40, so that an annular chamber 54 is formedbetween the support member 52and the tubular wall of container 56. The chamber 54 has an opening 56which may be connected by a conduit 58 to the various connections orterminations included at A, B and C, and which terminations may bedetermined in accordance with the same considerations set forth withregard to the embodiment of FIG. 1. Alternatively, as before, thechamber 54 may or may not be evacuated and may be provided with suitableabsorbent or adsorbent material for accommodating the removed gas.

The surface of the membrane 50 exposed to the chamber 54 is providedwith a gas-soluble coating 51 which may be of the same type as thecoating 19 described above with regard to the invention embodiment ofFIG. I.

The embodiment of FIG. 2 functions in a manner similar to that shown inFIG. 1. Eluate from the chromatographic system flows through tube 50which is formed from the permeable material. At least a portion of thegas dissolved in the eluate will pass or permeate through the permeablemembrane (such passage or permeation being enhanced by the increasedpermeability provided the membrane by the coating 51) through thesupport means 52 coaxially disposed about the permeable membrane 50, andinto the chamber 54, where, depending upon the termination of theconduit 58, the removed gas may be exhausted by a vacuum pump, vented tothe atmosphere, accommodated in the evacuated chamber 54, or absorbed oradsorbed by suitable material provided in the chamber 54.

FIGS. 3 and 4 show another embodiment of the invention which is similarto the embodiment previously shown in FIG. I. The apparatus, generallyindicated at 66, includes a first or upper section 62 and a lower secondsection 64 separated by a membrane 66. The membrane 66 differs from theequivalent structure in the embodiment shown in FIG. II in that themembrane is a single structural element which functions both as a gaspermeable membrane and as support means thus being a self-supporting gaspermeable membrane. Such membrane may be formed in several differentways, such as by having a support structure 67 comprised of a rigidporous material, e.g. sintered stainless steel, sintered brass, .orsintered TEFLON; with a first nonporous layer 69 of gas soluble and gaspermeable material, e.g. silicone sprayed or bonded on to the face ofthe porous material; and a second non-porous thin layer 73 sprayed orbonded onto the first layer. The second layer is preferably a chemicallyinert gas permeable material which will be in contact with the liquid tohave its gas concentration reduced.

As shown in FIG. 4, membrane 66 extends across the entire width of theapparatus in between the first section 62 and the second section 64; thesections being secured together by means of bolts (not shown) whichenter bolt holes 66 shown in FIG. 3.

A chamber 70 is formed in uppercavity 62, is provided with a tube 72which as indicated at A, B and C may be connected or terminated asdescribed hereinabove with regard to chambers 28 and 54of FIGS. 1 and 2,alternatively, the chamber 76 may be evacuated or not evacuated andfilled, as taught above, with adsorbent or absorbent material.

As may be seen in FIG. 3, the main difference in the construction ofsecond section 64 is the shape or configuration of the flow passage forthe liquid to have its gas concentration reduced. The cavity 71 formedin lower section 64 is provided with a spiral configuration, and hencein cooperation with membrane 66 provides flow passage 74 with a spiralconfiguration having an inlet 76 for the liquid and an outlet 78 throughwhich the liquid will leave the apparatus.

Further, it will be noted as shown in FIG. 4, the spiral cavity 71 isprovided with a V-shaped cross-sectional configuration to increase theamount of exposure of the liquid in the flow passage to the membrane 66,and the depth of the cavity is equal to the minimum depth necessary toallow the flow of a film of the liquid through the flow passage.Further, the spirally configured flow passage 74 is relatively long ascompared with its crosssectional area so that longitudinal mixing of theliquid is minimized.

The embodiment of the invention shown in FIG. 5 provides a serpentineconfiguration to the flow passage 82 for acommodating the liquid to haveits gas concentration reduced. The second section of the embodimentshown in FIG. 5, generally indicated at 80, has a cavity 81 formedtherein which is provided with a serpentine configuration so as toprovide the flow passage 82 with a serpentine configuration. The flowpassage is provided with an inlet port {84 and an outlet port 66, sothat liquid entering inlet port 64 flows through the serpentine flowpath to the outlet port 66.

The embodiment of the invention shown in FIG. 6 provides a labyrinthineflow passage for the liquid to have its gas concentration reduced, whichliquid flows through the apparatus. The second section of the apparatusshown in FIG. 6, generally indicated at 88, is provided with a cavity 89including a series of concentrically disposed circular cavities 96,which are separated by a series of concentrically disposed barrier wallsindicated at 98, the walls being pierced by a series of gates indicatedat 100 to connect the concentric flow paths so as to provide acontinuous flow path of the liquid from the inlet 92 to the outlet 94.The labyrinthine flow path is provided with an inlet port 92 and anoutlet port 94, which is connected by the labyrinthine flow passage 90.It will be understood by those skilled in the art that, for example,with regard to the consideration of possible solute peak broadening ofeluate from a chromatographic system, the labyrinthine flow passageconfiguration may be used more advantageously at relatively high eluateflow rates.

Operation of the embodiments shown in FIGS. 3 through 6 is substantiallythe same as the operation of the embodiments described above and shownin FIGS. 1 and 2.

Referring now to FIG. 7, there is shown an embodiment of the inventionsimilar to the embodiment of FIG. 2, and accordingly, correspondingstructure is correspondingly numbered. The embodiment of FIG. 7 differsfrom that of FIG. 2 by not including support means for the gas permeablemembrane 50. It has been found that, depending upon the pressure of theliquid to have its gas concentration reduced, and the amount of thepressure differential which may be established between the liquid andthe pressure in the chamber 54, the apparatus can functionsatisfactorily without any membrane support means. For example, it hasbeen found that with a sufficiently high vacuum established in thepressure chamber 54 tubing, known in the trade as FEP TEFLON, having asufficiently small diameter, functions satisfactorily without support inthe embodiment of FIG. 7. The coating 51 provided on the membrane 50 maybe the same as the aforementioned membrane coatings 19 of FIG. 1 and 51of FIG. 2.

With further regard to the embodiment of FIG. 7, while not completelyunderstood, it has been found that the tubular membrane 50, when coatedwith the gas-soluble coating 51 has the peculiar property of reducing,or tending to reduce, the gas concentration in the liquid flow streampassing through the tubing even if the coated surface of the membrane isexposed to the atmosphere and is not exposed to a pressure significantlylower than the pressure of the liquid. Accordingly, it will be expresslyunderstood that apparatus for reducing the gas concentration in a liquidcomprising only the gas permeable membrane provided with a coating ofmaterial in which the gas is significantly soluble, is within thecontemplation of the present invention and that patent protection issought therefor.

Referring again to FIG. 1, it will be also understood that it is withinthe contemplation of the present invention that the apparatus shown inFIG. I embodying the present invention may both include and not includethe support means 26. When not including the support means, the membrane18 would be unsupported but would be provided with the coating 19.Further, that it is within the contemplation of the present inventionthat the first membrane 18 of FIG. 1 be provided with the coating 19 andthe coated membrane surface be exposed to the atmosphere, and that suchstructure, as

with regard to the similar embodiment of FIG. 7, will reduce the gasconcentration in a liquid exposed to such coated membrane.

With regard to the gas permeable membranes, both flat and tubular, ithas been found that membranes having the property of abstracting anddissolving an appreciable quantity of the gas dissolved in a liquid incontact with the membranes, are particularly useful. More particularly,membranes of silicone rubber film, a silicone rubber-like material suchas GE. MEM 2 I 3; polyethylene; and fluorocarbon material, morespecifically a fluorinated ethylene-propylene co-polymer material suchas Dupont TEFLON FEP film; are particularly useful. Such membranematerials being particularly useful due to their resistance tocorrosion, for example the corrosive eluate from a chromatographiccolumn.

With regard to the support means of the various embodiments of thepresent invention, e.g. support 26 of FIG. 1 and support 52 of FIG. 2,it has been found that such support means may be comprised of sinteredstainless steel, sintered brass or sintered TEFLON; such materials beingresistant to corrosion from the eluate.

Similarly, it has been found that the housing or container for apparatusembodying the present invention, eg the sections 12 and 14 of FIG. 1 andcontainer 40 of FIG. 2, may be made advantageously of a suitablecorrosion resistant material, such as for example stainless steel.

With regard to the expression reduce or reducing the gas concentrationin a liquid," it will be understood by those skilled in the art thatsuch terms connote the understanding that depending upon various knownconditions, such as for example, the pressure level of the liquidincluding the gas, the nature of the liquid and gas included ordissolved therein, the subsequent utilization to be made of theliquid,.various amounts or percentages of the gas may be removed, hence,the expression reduce or reducing the gas concentration" is used toconnote these relative considerations.

It will be noted by those skilled in the art that when the apparatus ofthe present invention set forth above is used in a chromatographicsystem, it does not require separate treatment of the eluate other thanthe eluate flow through a predetermined flow passage. No boiling orother treatment of the eluate is necessary. Further, the flow path ofthe eluate is relatively undisturbed and unimpeded by the apparatus ofthe invention. The dimensions of the flow path can readily be adjustedto provide adequate surface area for contact or exposure of the eluatewith the permeable membrane while allowing sutficient velocity for theoperation of the chromatographic process.

It will also be noted that once the gas has been separated from theeluate, the gas is removed and hence is prevented from recombining withthe eluate.

It will be further noted that only the gas from the eluate will passthrough the permeable membrane, while none of the eluate will passthrough the membrane. Therefore, the associated apparatus forcontrolling the pressure in the pressure chamber can operateindependently of corrosive characteristics of the eluate.

It will also be noted that the flow path of the eluate need not beagitated or otherwise unnecessarily disturbed. Therefore, a minimum oflongitudinal mixing of the eluate is produced and it is possible topreserve the integrity of the eluate content distribution which oftencontains peaks or zones of solute.

it will be understood that various changes in the details, materials andarrangements of parts which have been herein described and illustratedin order to explain the nature of the invention may be made by thoseskilled in the art within the principle and scope of the invention asexpressed in the appended claims.

I claim: 1. Gas removing apparatus comprising: a housing having aplurality of openings formed therein; tubular flow means within saidhousing having an inlet and outlet; inlet means for connecting said flowmeans inlet to a chromatographic column having a solvent with gasdissolved therein through a path free of introduced, undissolved gas;and outlet means for connecting the flow means outlet to an analyzingdevice; said tubular flow means including membrane means for loweringthe dissolved gas concentration of the solvent to a level below thesaturation level of the gas in the solvent; said membrane meansincluding a membrane which is more permeable to the gas than to thesolvent and a coat on said membrane in which said gas is soluble;

said membrane having a first side and a second side;

said first side being positioned to contact said solvent and said secondside contacting said coat.

2. Gas removing apparatus according to claim 1 in which said coat is afilm of liquid in which said gas is appreciably soluble.

3. Gas removing apparatus according to claim 2 in which said film ofliquid is a film of light silicone.

4. Gas removing apparatus according to claim 2 in which said film ofliquid is a film ofa fluorosilicone'liquid.

5. Gas removing apparatus according to claim 1 in which said coat is afilm of solid silicone compound.

6. Gas removing apparatus according to claim 1 in which said coat is afilm of solid fluorosilicone compound.

7. Gas removing apparatus according to claim 1 in which:

said housing further includes a compartment adjacent to the membrane;

said chromatographic apparatus further includes pressure means forcreating a pressure in said compartment less than the pressure withinsaid tubular flow means, whereby gas is removed from said solvent insaid flow means.

8. Gas removing apparatus according to claim 7 further including pumpmeans for evacuating said compartment to provide the pressuredifferential.

9. Gas removing apparatus according to claim 8 in which said membraneadjacent to said compartment is elongated and curved with a largesurface area extending over a narrow section of said compartment.

10. Gas removing apparatus according to claim 9 in which the length ofsaid flow means is large compared to its width.

111. Gas removing apparatus according to claim 10 in which said membraneis self-supporting and said pump means includes a means for creating arelatively large pressure differential in said compartment.

12. Gas removing apparatus according to claim 10 in which said membraneis thin and said flow means further includes a porous member betweensaid membrane and said compartment supporting said membrane thereover.

13. Gas removing apparatus according to claim 10 in which said coat is afilm of liquid in which said gas is appreciably soluble.

14. Gas removing apparatus according to claim 13 in which said film ofliquid is a film of light silicone.

15. Gas removing apparatus according to claim 13 in which said film ofliquid is a film of fluorosilicone liquid.

16. Gas removing apparatus according to claim 10 in which said coat is afilm of solid silicone compound.

117. Gas removing apparatus according to claim it) in which said coat isa film of solid fluorosilicone compound.

18. Gas removing apparatus according to claim 1 in which:

said housing further includes a compartment adjacent to said membrane;

said compartment including means for sorbing said gas in said chamber.

19. Gas removing apparatus according to claim 18 in which said means forsorbing includes an absorbent material.

20. Gas removing apparatus according to claim 18 in which said means forsorbing includes adsorbent material.

2ll. Gas removing apparatus according to claim 19 in which said coat isa film of liquid in which said gas is appreciably soluble.

22. Gas removing apparatus according to claim 21 in which said film ofliquid is a film of light silicone.

23. Gas removing apparatus according to claim 21 in which said film ofliquid is a film of fluorosilicone liquid.

24. Gas removing apparatus according to claim 19 in which said coat is afilm of solid silicone compound.

25. Gas removing apparatus according to claim 19 in which said coat is afilm of solid fluorosilicone compound.

26. Gas removing apparatus according to claim 20 in which said coat is afilm of liquid in which gas is appreciably soluble.

27. Gas removing apparatus according to claim 26 in which said film ofliquid is a film of light silicone.

28. Gas removing apparatus according to claim 26 in which said film ofliquid is a film of fluorosilicone liquid.

29. Gas removing apparatus according to claim 20 in which said coat is afilm of solid silicone compound.

30. Gas removing apparatus according to claim 20 in which said coat is afilm of solid fluorosilicone compound.

1. Gas removing apparatus comprising: a housing having a plurality ofopenings formed therein; tubular flow means within said housing havingan inlet and outlet; inlet means for connecting said flow means inlet toa chromatographic column having a solvent with gas dissolved thereinthrough a path free of introduced, undissolved gas; and outlet means forconnecting the flow means outlet to an analyzing device; said tubularflow means including membrane means for lowering the dissolved gasconcentration of the solvent to a level below the saturation level ofthe gas in the solvent; said membrane means including a membrane whichis more permeable to the gas than to the solvent and a coat on saidmembrane in which said gas is soluble; said membrane having a first sideand a second side; said first side being positioned to contact saidsolvent and said second side contacting said coat.
 2. Gas removingapparatus according to claim 1 in which said coat is a film of liquid inwhich said gas is appreciably soluble.
 3. Gas removing apparatusaccording to claim 2 in which said film of liquid is a film of lightsilicone.
 4. Gas removing apparatus according to claim 2 in which saidfilm of liquid is a film of a fluorosilicone liquid.
 5. Gas removingapparatus according to claim 1 in which said coat is a film of solidsilicone compound.
 6. Gas removing apparatus according to claim 1 inwhich said coat is a film of solid fluorosilicone compound.
 7. Gasremoving apparatus according to claim 1 in which: said housing furtherincludes a compartment adjacent to the membrane; said chromatographicapparatus further includes pressure means for creating a pressure insaid compartment less than the pressure within said tubular flow means,whereby gas is removed from said solvent in said flow means.
 8. Gasremoving apparatus according to claim 7 further including pump means forevacuating said compartment to provide the pressure differential.
 9. Gasremoving apparatus according to claim 8 in which said membrane adjacentto said compartment is elongated and curved with a large surface areaextending over a narrow section of said compartment.
 10. Gas removingapparatus according to claim 9 in which the length of said flow means islarge compared to its width.
 11. Gas removing apparatus according toclaim 10 in which said membrane is self-supporting and said pump meansincludes a means for creating a relatively large pressure differentialin said cOmpartment.
 12. Gas removing apparatus according to claim 10 inwhich said membrane is thin and said flow means further includes aporous member between said membrane and said compartment supporting saidmembrane thereover.
 13. Gas removing apparatus according to claim 10 inwhich said coat is a film of liquid in which said gas is appreciablysoluble.
 14. Gas removing apparatus according to claim 13 in which saidfilm of liquid is a film of light silicone.
 15. Gas removing apparatusaccording to claim 13 in which said film of liquid is a film offluorosilicone liquid.
 16. Gas removing apparatus according to claim 10in which said coat is a film of solid silicone compound.
 17. Gasremoving apparatus according to claim 10 in which said coat is a film ofsolid fluorosilicone compound.
 18. Gas removing apparatus according toclaim 1 in which: said housing further includes a compartment adjacentto said membrane; said compartment including means for sorbing said gasin said chamber.
 19. Gas removing apparatus according to claim 18 inwhich said means for sorbing includes an absorbent material.
 20. Gasremoving apparatus according to claim 18 in which said means for sorbingincludes adsorbent material.
 21. Gas removing apparatus according toclaim 19 in which said coat is a film of liquid in which said gas isappreciably soluble.
 22. Gas removing apparatus according to claim 21 inwhich said film of liquid is a film of light silicone.
 23. Gas removingapparatus according to claim 21 in which said film of liquid is a filmof fluorosilicone liquid.
 24. Gas removing apparatus according to claim19 in which said coat is a film of solid silicone compound.
 25. Gasremoving apparatus according to claim 19 in which said coat is a film ofsolid fluorosilicone compound.
 26. Gas removing apparatus according toclaim 20 in which said coat is a film of liquid in which gas isappreciably soluble.
 27. Gas removing apparatus according to claim 26 inwhich said film of liquid is a film of light silicone.
 28. Gas removingapparatus according to claim 26 in which said film of liquid is a filmof fluorosilicone liquid.
 29. Gas removing apparatus according to claim20 in which said coat is a film of solid silicone compound.
 30. Gasremoving apparatus according to claim 20 in which said coat is a film ofsolid fluorosilicone compound.